Wireless power-transmission apparatus and wireless power-transmission method

ABSTRACT

A wireless power-transmission apparatus includes at least one antenna element disposed at a specific position in a three-dimensional space having a predetermined shape and size, to transmit a power transmission beam, an acquirer to acquire an inclination angle of the antenna element to a plane direction of a reference plane and a height of the antenna element to the reference plane, and a controller to control at least one of antenna power and a power transmission direction of the power transmission beam so that interference power of the power transmission beam toward an outside of the three-dimensional space becomes equal to or smaller than a predetermined allowable value when the antenna element is disposed at the acquired inclination angle and height.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2018-136006, filed on Jul. 19,2018, the entire contents of which are incorporated herein by reference.

FIELD

Embodiments of the present disclosure relate to a wirelesspower-transmission apparatus and a wireless power-transmission method.

BACKGROUND

A power-transmission beam direction control technique is known, whichdetects the position and posture of a power transmission satellite usinga navigation sensor and controls a transmission method for a powertransmission beam based on position information of a power receptionfacility.

In the above-described known power-transmission beam direction controltechnique, the influence of interference given to other wirelessequipment from the power transmission beam is not considered. Therefore,the interference may be given to wireless communication of otherwireless equipment present in the vicinity of a power receiver forreceiving the power transmission beam.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram schematically showing the configuration of awireless power-transmission apparatus according to a first embodiment;

FIG. 2 is a figure showing one operation mode of the wirelesspower-transmission apparatus 1 according to the first embodiment;

FIG. 3 is a figure showing that a power transmission antenna hasdirectivity in a single direction.

FIG. 4 is a figure showing characteristic curves of power densityS_(sphere) and S_(bottom) to an angle θ;

FIG. 5 is a figure explaining an antenna gain of a power transmissionantenna;

FIG. 6 is a figure showing an operational principle of a phased arrayantenna having antenna elements arranged on a one-dimensional line;

FIG. 7A shows an antenna gain;

FIG. 7B shows an array factor;

FIG. 7C shows an array gain;

FIG. 8 is a block diagram schematically showing the configuration of awireless power-transmission apparatus according to a second embodiment;

FIG. 9 is a figure showing an example of an indoor space having aplurality of rooms;

FIG. 10 is a block diagram schematically showing the configuration of awireless power-transmission apparatus according to a fourth embodiment;and

FIG. 11 is a figure showing an example of installation of aninterference power measurer at an end of a three-dimensional space.

DETAILED DESCRIPTION

According to the present embodiment, there is provided a wirelesspower-transmission apparatus including:

at least one antenna element disposed at a specific position in athree-dimensional space having a predetermined shape and size, totransmit a power transmission beam;

an acquirer to acquire an inclination angle of the antenna element to aplane direction of a reference plane and a height of the antenna elementto the reference plane; and

a controller to control at least one of antenna power and a powertransmission direction of the power transmission beam so thatinterference power of the power transmission beam toward an outside ofthe three-dimensional space becomes equal to or smaller than apredetermined allowable value when the antenna element is disposed atthe acquired inclination angle and height.

Hereinbelow, embodiments will be explained with reference to theaccompanying drawings. In the present specification and the accompanyingdrawings, for easy understanding and simplicity in drawings, theexplanation and drawings are made with omitting, modifying orsimplifying part of the configuration. Moreover, in the accompanyingdrawings of the present specification, for simplicity in drawings andeasy understanding, the scale, the ratio of height to width, etc. aremodified to be exaggerated from those of actual ones.

First Embodiment

FIG. 1 is a block diagram schematically showing the configuration of awireless power-transmission apparatus 1 according to a first embodiment.The wireless power-transmission apparatus 1 of FIG. 1 is provided with afunction of transmitting a power transmission beam to a power receivernot shown. The power receiver may, for example, be various sensors. Thewireless power-transmission apparatus 1 of FIG. 1 is provided with atleast one antenna element (hereinafter, also referred to as a powertransmission antenna) 2 for power transmission, an acquisition unit 3,and a control unit 4, as essential components.

The power transmission antenna 2 is disposed at a predetermined positionin a three-dimensional space of a predetermined shape and size, to emita power transmission beam. The three-dimensional space is typically anindoor space of a building. The building may be a business facility suchas a factory, or a house. Moreover, the three-dimensional space may havea plurality of partitioned small spaces. The predetermined position maybe any position in the three-dimensional space. For example, the powertransmission antenna 2 may be disposed at any position on a ceilingsurface or a wall surface in the indoor space.

The power transmission antenna 2 may, for example, a phased arrayantenna, as described later. The phased array antenna has a plurality ofantenna elements 2, which can control directivity (power transmissiondirection and gain) by adjusting the phase of a current of each antennaelement 2.

The acquisition unit 3 acquires an inclination angle of the powertransmission antenna 2 to a plane direction of a reference plane and aheight of the power transmission antenna 2 to the reference plane. Thereference plane is, for example, a ground surface or a floor surface.The acquisition unit 3 may acquire an angle measured by an anglemeasurer 5 that measures the inclination angle of the power transmissionantenna 2 and a height measured by a height measurer 6 that measures theheight of the power transmission antenna 2. The angle measurer 5 and theheight measurer 6 are, for example, directly attached to or arranged inthe vicinity of the power transmission antenna 2. The angle measurer 5can be configured with an acceleration sensor, a gyros sensor, etc. Theheight measurer 6 can be configured with a laser distance sensor. Theangle measurer 5 and the height measurer 6 may not necessarily beprovided inside the wireless power-transmission apparatus 1 of FIG. 1.

The acquisition unit 3 may read out to acquire the inclination angle andheight of the power transmission antenna 2 stored in the storage unit 7.The storage unit 7 stores the inclination angle and the height after theinstallation or adjustment of the power transmission antenna 2. Sincethe power transmission antenna 2 is usually fixed, the inclination angleand the height do not vary after the installation or adjustment.Therefore, at the stage of completion of the installation of the powertransmission antenna 2, the inclination angle and height of the powertransmission antenna 2 may be stored in the storage unit 7, and then theacquisition unit 3 may read out the inclination angle and height fromthe storage unit 7, as required.

The reason why the acquisition unit 3 acquires the inclination angle andheight of the power transmission antenna 2 is that, when the inclinationangle and height of the power transmission antenna 2 vary, the powertransmission direction and range of the power transmission beam change.In more specifically, as the inclination angle of the power transmissionantenna 2 to the plane direction of the reference plane becomes larger,the power transmission beam is transmitted further away. Moreover, asthe height of the power transmission antenna 2 is higher than thereference plane, the received power on the reference plane reduces,although the power transmission range of the power transmission beambecomes wider.

Although the wireless power-transmission apparatus 1 of FIG. 1 isprovided with the angle measurer 5, the height measurer 6, and thestorage unit 7, these are not essential components. The acquisition unit3 may acquire the inclination angle and height of the power transmissionantenna 2 via any means. For example, the wireless power-transmissionapparatus 1 of FIG. 1 may be provided with an input unit not shown, andvia the input unit, an inclination angle and a height measured by ameasuring device installed separately may be input. Or the inclinationangle and height measured by the measuring device installed separatelymay be fetched in the acquisition unit 3 via wireless or wiredconnection.

The control unit 4 controls at least one of the antenna power and powertransmission direction of the power transmission beam so that theinterference power of the power transmission beam toward the outside ofthe three-dimensional space becomes equal to or smaller than apredetermined allowable value when the power transmission antenna 2 isinstalled at the inclination angle and height acquired by theacquisition unit 3.

The allowable value is set in accordance with the specification andwireless mode of wireless equipment installed outside thethree-dimensional space. The specification and wireless mode of wirelessequipment are receiver sensitivity, an allowable interference leveldecided by the hardware and software of the wireless equipment, or arethose restricted in the standards and laws of wireless communication,etc.

The reason why the control unit 4 controls the antenna power of thepower transmission beam is that, as the antenna power is larger, theinterference power increases. Moreover, the reason why the control unit4 controls the power transmission direction of the power transmissionbeam is that, as the power transmission direction of the powertransmission beam is more apart from the plane direction of thereference plane, the power transmission beam is transmitted furtheraway. When the interference power of the power transmission beam towardthe outside of the three-dimensional space is larger than the allowablevalue, the antenna power may be set smaller or the power transmissiondirection of the power transmission beam may be set closer to the planedirection of the reference plane.

In addition to the above, the wireless power-transmission apparatus 1 ofFIG. 1 may have a communication unit 8 and a communication antenna 9.The communication unit 8 transmits and receives terminal ID informationto and from a power receiver not shown to which power is to betransmitted, receives a power transmission request from the powerreceiver, and so on, via the communication antenna 9. The communicationantenna 9 and the power transmission antenna 2 may be united to eachother.

In addition to the above, the wireless power-transmission apparatus 1 ofFIG. 1 may have a plurality of quadrature detectors 11 as a plurality ofpropagation-path estimation systems 10. The wireless power-transmissionapparatus 1 of FIG. 1 transmits a signal that instructs transmission ofa propagation-path estimation signal, to a power receiver that has madethe power transmission request. The power receiver that has received theabove-described signal transmits the propagation-path estimation signal.When the propagation-path estimation signal from the power receiver isreceived by the plurality of power transmission antennas 2, theplurality of quadrature detectors 11 each separate the receivedpropagation-path estimation signal into an in-phase component and aquadrature component to acquire propagation path information of phaseand amplitude per system. The conversion of in-phase and quadraturecomponents of each propagation-path estimation signal into thepropagation path information of phase and amplitude is performed by acalculation unit 12 in the wireless power-transmission apparatus 1 ofFIG. 1. A calculation result of the calculation unit 12 is stored in thestorage unit 7. The estimated propagation-path estimation informationmay be substituted with position and direction information of the powerreceiver estimated with an arrival direction estimation technique. Theacquisition unit 3, the control unit 4, and the storage unit 7 configurethe control system 13.

In addition to the above, the wireless power-transmission apparatus 1 ofFIG. 1 is provided with a signal source 14 to generate apower-transmission signal and a distributor 15 to distribute thepower-transmission signal. Moreover, the wireless power-transmissionapparatus 1 of FIG. 1 is provided with a plurality of variable phaseshifters 18 and the corresponding plurality of variable amplifiers 19,as a plurality of power transmission systems 17. The plurality of powertransmission systems 17, the plurality of propagation-path estimationsystems 10, and the plurality of power transmission antennas 2 areconnected to a high-frequency switch 16. The high-frequency switch 16selects whether to transmit the signals from the plurality of powertransmission systems 17 to the plurality of power transmission antennas2 or transmit the received signals from the plurality of powertransmission antennas 2 to the plurality of propagation-path estimationsystems 10.

The power transmission signal generated by the signal source 14 isdistributed by the distributor 15 to the plurality of power transmissionsystem 17. In each power transmission system 17, the variable phaseshifter 18 controls the phase of the power transmission signal and thevariable amplifier 19 controls the amplitude of the power transmissionsignal. In this way, each power transmission system 17 generates aradiation pattern for the power transmission beam. A phase shift valuein each variable phase shifter 18 and a gain of each variable amplifier19 are calculated by the calculation unit 12 based on the propagationpath information received by the plurality of propagation-pathestimation systems 10. The operation of each component in the wirelesspower-transmission apparatus 1 of FIG. 1 is controlled by the controlunit 4.

In the following, an explanation will be made about the wirelesspower-transmission apparatus 1 that measures the inclination angle andheight of the power transmission antenna 2, with the angle measurer 5and the height measurer 6, respectively, and changes the powertransmission state based on these measurement results, to make theinterference power on the outside of the three-dimensional space equalto or smaller than the predetermined allowable value.

FIG. 2 is a figure showing one operation mode of the wirelesspower-transmission apparatus 1 according to the first embodiment. Apower transmission antenna 2 of FIG. 2 is installed parallel, in itsplane direction, to the ground surface at a height H from the groundsurface. The power transmission direction of a power transmission beamto be transmitted from the power transmission antenna 2 has an openingangle θ to the direction of normal to the reference plane.

The power transmission antenna 2 of FIG. 2 is, as shown in FIG. 3 indetail, a power transmission antenna 2 having directivity in a singledirection. A power radiation pattern G of the power transmission antenna2 of FIG. 3 can, for example, be expressed by the following expression(1).

G=Gi cos^(i)θ  (1)

In the expression (1), 0 is an angle within the range of −90°≤θ≤90°, Gibeing a maximum gain of the power transmission antenna 2 in accordancewith the order i. As the order i is larger, the radiation pattern has ahigher gain and a narrower width, and the maximum gain when i is two isabout 7.8 dBi, with a half-value angle of about 90°, showing thecharacteristics similar to an actual patch antenna. In the followingexample, the radiation pattern at the order of i=2 is assumed.

In general, an antenna gain is defined on the spherical surface of asphere that encloses an antenna. However, in a real operation mode, anobject to be interfered by radio waves may be present at an almost sameheight as the antenna. Power density S_(sphere) on a sphere with aradius of H from the antenna is expressed by the following expression(2).

$\begin{matrix}{S_{sphere} = {\frac{{KP}_{ant}G}{4\pi \; H^{2}} = \frac{{KP}_{ant}G_{2}\cos^{2}\theta}{4\pi \; H^{2}}}} & (2)\end{matrix}$

In the expression (2), P_(ant) is the total power fed to the powertransmission antenna 2, referred to as antenna power, and a constant Kis a coefficient in consideration of the influence of radio wavereflection depending on environments. Using the angle θ, the height H ofthe power transmission antenna 2, and a distance D between the positionof a perpendicular line, on the ground surface, from the center of thepower transmission antenna 2 to the ground surface, and the position(observation point) of a power transmission beam, on the ground surface,which propagates at the angle θ from the power transmission antenna 2, adirect distance R from the center of the power transmission antenna 2 tothe observation point is given by the following expression (3).

$\begin{matrix}{R = {\frac{H}{\cos \mspace{11mu} \theta} = {\frac{D}{\sin \mspace{11mu} \theta} = \sqrt{H^{2} + D^{2}}}}} & (3)\end{matrix}$

Therefore, the power density observed at the observation point on theground surface in a direction of the angle θ is given by the followingexpression (4), using the above-described direct distance R.

$\begin{matrix}{S_{bottom} = {\frac{{KP}_{ant}G}{4\pi \; R^{2}} = {\frac{{KP}_{ant}G}{4\pi \; \left( \frac{H}{\cos \mspace{11mu} \theta} \right)^{2}} = \frac{{KP}_{ant}G_{2}\cos^{4}\theta}{4\pi \; H^{2}}}}} & (4)\end{matrix}$

FIG. 4 is a figure showing characteristic curves cb1 and cb2 of powerdensity S_(sphere) and S_(bottom) to the angle θ. The characteristiccurves cb1 and cb2 have been normalized with a value of S_(sphere) inthe direction of 0°. As understood from the expressions (2) and (4), andFIG. 4, in comparison with the characteristics on the sphere, the powerdensity on the ground surface rapidly reduces on the order of cos⁴θ asthe angle θ increases. Here, the following expression (5) is establishedbetween the horizontal distance D, the height H, and the angle θ.

D=H tan θ  (5)

When θ is gradually close to 90°, D tends to increase. In other words,as the object to be interfered is further away from the wirelesspower-transmission apparatus 1 in the direction of the horizontaldistance D, it is expected that the influence of interference isreduced.

When the antenna gain at the installation of the antenna of FIG. 3,given by the expression (1), is set as a reference, as shown in FIG. 5,in the case where the power transmission antenna 2 is installed inclinedat an inclination angle Δθ to the direction of the ground surface (it isdefined that the angle has a positive value in a clockwise direction tothe direction of the ground surface), an effective antenna gain G can beexpressed by the following expression (6).

G′=G ₂ cos²(θ−Δθ)  (6)

However, the expression (6) has a condition of −90°≤θ−Δθ90°. Therefore,as the inclination angle is larger, the direction in which the maximumgain is given is oriented further toward the direction of the horizontaldistance, and hence radio waves reach further away, so that interferencemay occur even if an enough distance is taken.

Moreover, as the antenna installation height H becomes higher, the rangeon the bottom surface where radio waves are radiated becomes wider, andhence the probability of interference increases. Therefore, in order tomake it possible to restrict the influence of interference topotentially present objects to be interfered, with no need to grasptheir operational states, it is important to control the transmissioncondition so as to suppress the power density on the outside of apredetermined range within a predetermined value, in accordance with theinclination angle and installation height of the power transmissionantenna 2.

As the policy for suppressing the power density on the outside of thepredetermined range within the predetermined value, the followingexpression (7) can be used.

$\begin{matrix}{P_{int} = \frac{{KP}_{ant}G_{T_{x}}G_{R_{x}}}{L_{pol}L_{obj}L_{path}}} & (7)\end{matrix}$

The above expression P_(int) expresses the interference power at a givenhorizontal distance D, calculated based on the Friis transmissionequation, K and P_(ant) being as described above, and GTx expressing anantenna gain used in a power transmission apparatus, which is a functiondepending on the angle θ and the antenna inclination angle Δθ like theexpression (6). In practice, a calculation result obtained byelectromagnetic simulation or an experimental value obtained bydirectivity measurements is used as a reference antenna gain.

A sign GR_(x) expresses an antenna gain of an object to be interfered.Although, in practice, this is also a function that depends on angularinformation, it is desirable to employ, in calculation here, theantenna-gain maximum value defined in the standards, specifications,laws, etc. with respect to a wireless system that may be an object to beinterfered. This is because, for the interference to a wireless systempotentially present, the worst conditions should be considered toperform calculation on the assumption of overestimation.

A sign L_(pol) expresses polarization loss between the wirelesspower-transmission apparatus 1 and the antenna of an object to beinterfered. For example, when both have antennas of the samepolarization, L_(pol) is 0 dB, whereas, in the case where one has anantenna of linear polarization and the other has an antenna of circularpolarization, L_(pol) is 3 dB.

A sign L_(obj) expresses transmission loss caused by an object presentin a radio wave path. The transmission loss has a value per object, suchas, transmission loss caused by a wall is 17 dB and transmission losscaused by glass is 4 dB.

A sign L_(path) is propagation loss that depends on an optical pathlength, given by the following expression (8).

$\begin{matrix}{L_{path} = \left( \frac{4\pi \; R}{\lambda} \right)^{2}} & (8)\end{matrix}$

In the above expression, λ is the wavelength of a power transmissionsignal and R is given by the expression (3). In calculation ofinterference power, besides the Friis transmission equation in theexpression (6), a proper channel model can be selected in accordancewith the installation environment of the wireless power-transmissionapparatus 1.

When the predetermined range (horizontal distance) is D_(thr), byobtaining the maximum value P_(int,max) of the expression (7) in a rangeequal to or larger than D_(thr), which satisfies the followingexpression (9) with a predetermined allowable value P_(thr), theinterference power on the outside of the predetermined range can be madeto fall within the predetermined value.

P _(int,max) ≤P _(thr)  (9)

The value P_(thr) is decided, for example, based on the specificationssuch as receiver sensitivity and allowable interference level, definedin the standards, specifications, laws, etc. for a wireless system thatuses a frequency band (channel) which includes the frequency of a powertransmission signal of the wireless power-transmission apparatus 1 orwhich is in the vicinity of this frequency, and that is deemed to be anobject to be interfered. In order to satisfy the condition of theexpression (9) with control by the wireless power-transmission apparatus1, the antenna power P_(ant) or the gain GT_(x) of the powertransmission antenna 2 is varied, as understood from the expression (7).

The antenna power P_(ant) can be varied by controlling the output powerof the signal source 14 or the gain of the variable amplifiers 19 of thetransmission systems 17, in the wireless power-transmission apparatus 1of FIG. 1. Therefore, when P_(int,max) exceeds P_(thr), as understoodfrom the expression (7), since P_(int) is a linear function of P_(ant),P_(ant) may be linearly reduced to satisfy the expression (9).

For the gain GT_(x) of the power transmission antenna 2, although thereare various control methods, a method using a phased array antenna willbe explained hereinbelow. The phased array antenna forms a beam having ahigh gain in a desired direction by appropriately adjusting the phase ofa signal supplied to a plurality of arranged antennas. FIG. 6 is afigure showing an operational principle of a phased array antenna havingantenna elements 2 arranged on a one-dimensional line. It is definedhere that the phased array antenna has N antenna elements 2 and theantennas elements 2 have the same directivity given by the expression(1), with the equal distance d between the adjacent elements. An arraygain (power radiation pattern) G_(array) of the phased array antenna isgiven by the following expression (10) when the phase of a signalsupplied to an n-th antenna element 2 is ψn and the amplitude of signalssupplied to all antenna elements 2 is equally 1/√N.

$\begin{matrix}{{G_{array}(\theta)} = {{G(\theta)}{{\sum\limits_{n = 1}^{N}\frac{e^{j\; \psi_{n}}e^{{{jk}{({n - 1})}}{dsin}\; \theta}}{\sqrt{N}}}}^{2}}} & (10)\end{matrix}$

In the expression (10), k is a wavenumber. In the case of maximizing thegain in the direction of a desired angle θ′, the phase ψn of the signalsupplied to the n-th antenna element 2 is given by the followingexpression (11).

ψ_(n) =−k(n−1)d sin θ′  (11)

By putting the above-described expression (11) into the expression (10),the array gain is given by the following expression (12).

$\begin{matrix}{{G_{array}\left( {\theta,\theta^{\prime}} \right)} = {{{G(\theta)}{{\sum\limits_{n = 1}^{N}\frac{e^{{{jk}{({n - 1})}}{d{({{\sin \mspace{11mu} \theta} - {\sin \; \theta^{\prime}}})}}}}{\sqrt{N}}}}^{2}} = {{G(\theta)}{{{AF}\left( {\theta,\theta^{\prime}} \right)}}^{2}}}} & (12)\end{matrix}$

In the expression (12), the term of total sum in the absolute value isreferred to as an array factor AF that is a function depending on theangle θ and the desired angle θ′. The array gain G_(array) is a productof the gain G of a single antenna element 2 and the absolute valuesquared of the array factor AF.

FIGS. 7A, 7B and 7C show the results of numerical analysis of thecharacteristics of antenna gain, array factor and array gain,respectively, to the angle θ. In the numerical analysis, the number ofantennas is 64 and the element distance d is set to a half-wavelength.FIG. 7B shows the characteristics at the desired angle θ′ in theexpression (11) set to 0, 15, 30 and 45 degrees, from which it is foundthat the array factor is maximized at each desired angle. Thearray-factor maximum value depends on the number of antennas but takesthe same value irrespective of the desired angle. Since thecharacteristics of FIGS. 7A and 7B are both given in decibel, the arraygain of FIG. 7C can be expressed with the sum of the characteristics ofantenna gain and array factor in FIGS. 7A and 7B, respectively, in whichthe envelope that connects the maximum values of array gain atrespective angles can be expressed with a pattern that is the sum of theantenna gain and the maximum values of array factor.

According to the above, a transmission gain GTx can also be varied byusing the phased array antenna. Therefore, when P_(int,max) exceedsP_(thr), a method which can be employed is to restrict the angle θ′ forforming a desired beam in the range that satisfies the expression (9).When the expression (9) cannot be satisfied only by restricting thedesired angle θ′, the antenna power P_(ant) can also be reduced at thesame time.

What is discussed in the above explanation is only the phased arrayantenna having antenna elements arranged in one dimension with the equaldistance therebetween. However, the above discussion can be extended tophased array antennas having antenna elements arranged ontwo-dimensional plane and on three-dimensional solid, and a phased arrayantenna of an aperiodic configuration.

As described above, in the first embodiment, since the powertransmission direction and interference power of a power transmissionbeam vary based on the inclination angle and installation height of theantenna elements 2, by using a phased array antenna for which theantenna power and power transmission direction of a power transmissionbeam are controllable, at least one of the antenna power and powertransmission direction of the phased array antenna is controlled so thatthe interference power to the outside of the three-dimensional spacecaused by the power transmission beam becomes equal to or smaller thanthe predetermined allowable value. Accordingly, the interference powerto the outside of the three-dimensional space can be restricted to beequal to or smaller than the predetermined allowable value, so that apossible adverse influence of the power transmission beam to wirelesscommunication of wireless equipment arranged on the outside of thethree-dimensional space can be reduced. Moreover, since the antennapower and the power transmission direction can be controlled easily byusing the phased array antenna, the interference power to the outside ofthe three-dimensional space can also be relatively easily restricted tobe equal to or smaller than the predetermined allowable value.

Second Embodiment

The example explained in the above-described first embodiment is tocontrol at least one of the antenna power and power transmissiondirection of the power transmission antenna 2 so that the interferencepower to the outside of the three-dimensional space becomes equal to orsmaller than the predetermined allowable value. The three-dimensionalspace is, for example, an indoor space in which the power transmissionantenna 2 is installed. In this case, the power transmission antenna 2is disposed on the indoor ceiling surface, wall surface, pillars,framework, etc.

Various communication equipment arranged in the same indoors are usuallymanaged by the same administrator, owner or operator. By contrast, inthe indoors and outdoors, the administrators, owners or operators areoften different from each other. Therefore, the radio waves transmittedand received in the indoor space should be prevented from givinginterference to the outdoor communication equipment.

Accordingly, in the present embodiment, the interference to the outdoorsis restricted to be equal to or smaller than a predetermined value insuch a manner that a power transmission beam is allowed to reach only anend of the indoor space from a position on a reference plane just underthe wireless power-transmission apparatus 1 installed in the indoorspace.

FIG. 8 is a block diagram schematically showing the configuration of awireless power-transmission apparatus 1 according to a secondembodiment. The wireless power-transmission apparatus 1 of FIG. 8 isprovided with a distance measurer 21 added to the configuration ofFIG. 1. The distance measurer 21 measures the distance from the wirelesspower-transmission apparatus 1 to an end of the indoor space.

For the distance measurer 21, for example, a laser range finder is used.The end of the indoor space is desirably an end under the worstcondition with the maximum interference power. The end is located at anygiven position of the interface between the indoor space and theoutdoors.

The distance measurer 21 is not always necessarily built in the wirelesspower-transmission apparatus 1. In the installation of the wirelesspower-transmission apparatus 1 in the indoor space, the distance fromthe wireless power-transmission apparatus 1 to the end of the indoorspace may be measured with a laser range finder or the like and storedin the storage unit 7 of the wireless power-transmission apparatus 1. Inthis case, the control unit 4 may read out the distance stored in thestorage unit 7 to control at least one of the antenna power and powertransmission direction of a power transmission beam so that theinterference power to the outside of the indoor space becomes equal toor smaller than the allowable value, based on the inclination angle andheight of the power transmission antenna 2, and also the above-describeddistance.

In the case where the indoor space includes a plurality of roomsportioned by walls or the like as shown in FIG. 9, a distance measurer21 such as a laser range finder cannot measure the distance from thewireless power-transmission apparatus 1 to the end of the indoor space.In this case, based on design drawings including information on thesize, layout, etc. of the indoor space, the above-described distance maybe acquired and stored in the storage unit 7. Moreover, since thetransmittance of radio waves varies depending on the materials of theceiling, wall and floor surfaces, and the like, the transmittance may bepredicted from the materials of the wall surfaces and the like, to setthe transmission loss L_(obj) in the above-described expression (7). Asthe value of the transmission loss L_(obj) is larger, the influence ofinterference to the outside of the indoor space can be reduced further.

As described above, in the second embodiment, the distance from thewireless power-transmission apparatus 1 to the end of thethree-dimensional space is detected, and taking the distance intoconsideration, at least one of the antenna power and power transmissiondirection of a power transmission beam is controlled. Therefore, theinterference power on the outside of the three-dimensional space can bereduced further in consideration of the shape and size of thethree-dimensional space and the installation location of the wirelesspower-transmission apparatus 1 in the three-dimensional space.

Third Embodiment

In the wireless power-transmission apparatuses 1 of the first and secondembodiment, the antenna power and/or power transmission direction of apower transmission beam are/is controlled so that the interference powerto the outside of the three-dimensional space becomes equal to orsmaller than the allowable value. However, there may be cases where theinterference power does not become equal to or smaller than theallowable value no matter how the antenna power and/or powertransmission direction are/is controlled. In this case, the control unit4 may forcibly stop power transmission from the power transmissionantenna 2. In that case, it may be notified with some means that theinterference power does not become equal to or smaller than theallowable value. As for a specific notification means, the notificationmay be made with sounds or display, or a signal for notification may betransmitted to an administrator's PC or server in a wireless or wiredmanner.

Moreover, after stopping the transmission of a power transmission beamfrom the power transmission antenna 2, the control unit 4 may controlthe antenna power and/or power transmission direction of the powertransmission beam to examine whether the interference power becomesequal to or smaller than the allowable value, and if so, restart thetransmission of the power transmission beam from the power transmissionantenna 2.

As described above, in the third embodiment, in the case where theinterference power to the outside of the three-dimensional space doesnot become equal to or smaller than the allowable value even though theantenna power and/or power transmission direction of the powertransmission beam are/is controlled, the transmission of the powertransmission beam from the power transmission antenna 2 is forciblystopped, so that adverse influence of the interference power to wirelessequipment on the outside of the three-dimensional space can certainly beprevented.

Fourth Embodiment

A fourth embodiment proposes a positional measure in the case where theinterference power does not become equal to or smaller than theallowable value.

FIG. 10 is a block diagram schematically showing the configuration of awireless power-transmission apparatus 1 according to the fourthembodiment. The wireless power-transmission apparatus 1 of FIG. 10 isprovided with an antenna adjusting unit 22 added to the configuration ofFIG. 1. The antenna adjusting unit 22 adjusts at least one of theinclination angle and height of the power transmission antenna 2. Theexample which will be explained hereinbellow is that the antennaadjusting unit 22 can adjust the inclination angle and the heightseparately. However, only the inclination angle or only the height maybe adjusted, or the inclination angle and the height may be adjusted inlinkage with each other.

The antenna adjusting unit 22 has a rotation adjuster capable of varyingthe inclination angle of the power transmission antenna 2 and anelevation adjuster capable of varying the height of the powertransmission antenna 2.

The control unit 4 adjusts at least one of the inclination angle andheight of the power transmission antenna 2 using the antenna adjustingunit 22 in the case where the interference power does not become equalto or smaller than the allowable value even though at least one of theantenna power and power transmission direction of the power transmissionbeam is controlled. As described above, as the inclination angle of thepower transmission antenna 2 to the direction of the reference plane islarger, the power transmission beam is transmitted further away.Therefore, in order to restrict the interference power, it is preferableto make the inclination angle as smaller as possible. Moreover, as theheight of the power transmission antenna 2 is higher, the powertransmission range of the power transmission beam becomes wider.Therefore, in order to restrict the interference power, it is preferableto make lower the height of the power transmission antenna 2.

Furthermore, the control unit 4 may freely control, with no priority, atleast one of the antenna power and power transmission direction of thepower transmission beam, and at least one of the inclination angle andheight of the power transmission antenna 2, so that the interferencepower becomes equal to or smaller than the predetermined allowablevalue.

As described above, the fourth embodiment is provided with the antennaadjuster 22 that adjusts at least one of the inclination angle andheight of the power transmission antenna 2. Therefore, the interferencepower can be made equal to or smaller than the predetermined allowablevalue even in the case where the interference power does not becomeequal to or smaller than the predetermined allowable value only bycontrol of the antenna power and/or power transmission direction of thepower transmission beam, so that the frequency of forcibly stopping thepower transmission beam from the power transmission antenna 2 can bereduced.

Fifth Embodiment

The wireless power-transmission apparatus 1 in each of the first tofourth embodiments is to prevent the adverse influence of the powertransmission beam from the power transmission antenna 2 to the wirelessequipment installed on the outside of the three-dimensional space.However, practically, the magnitude of interference power leaked to theoutside of the three-dimensional space varies depending on the shape,size, presence or absence of partitions, materials of walls, ceilings,etc. of the three-dimensional space where the wirelesspower-transmission apparatus 1 is installed.

Accordingly, as shown in FIG. 11, an interference power measurer 23 formeasuring the interference power may be installed at an end of thethree-dimensional space. The interference power measurer 23 measures theinterference power at that position. FIG. 11 shows an example ofinstallation of the interference power measurer 23 only at one locationof the end of the three-dimensional space. However, the interferencepower measurer 23 may be installed at each of a plurality of locations.In particular, when there is a member such as glass which radio waveseasily pass through, it is desirable to install the interference powermeasurer 23 in the vicinity of that member.

The interference power measured by the interference power measurer 23 istransmitted to the control unit 4 in a wired or wireless manner. Thecontrol unit 4 controls at least one of the antenna power and powertransmission direction of the power transmission beam so that theinterference power measured by the interference power measurer 23becomes equal to or smaller than a predetermined allowable value.Moreover, as explained in the fourth embodiment, the control unit 4 maycontrol at least one of the inclination angle and height of the powertransmission antenna 2.

As described above, in the fifth embodiment, the interference powermeasurer 23 installed at the end of the three-dimensional space measuresinterference power at that location and compares the measuredinterference power with the allowable value, so that it is accuratelydetermined whether the interference power is equal to or smaller thanthe allowable value.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel methods and systems describedherein may be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the methods andsystems described herein may be made without departing from the spiritof the inventions. The accompanying claims and their equivalents areintended to cover such forms or modifications as would fall within thescope and spirit of the inventions.

1. A wireless power-transmission apparatus comprising: at least oneantenna element disposed at a specific position in a three-dimensionalspace having a predetermined shape and size, to transmit a powertransmission beam; an acquirer to acquire an inclination angle of theantenna element to a plane direction of a reference plane and a heightof the antenna element to the reference plane; and a controller tocontrol at least one of antenna power and a power transmission directionof the power transmission beam so that interference power of the powertransmission beam toward an outside of the three-dimensional spacebecomes equal to or smaller than a predetermined allowable value whenthe antenna element is disposed at the acquired inclination angle andheight.
 2. The wireless power-transmission apparatus of claim 1, whereinthe allowable value is set in accordance with a specification of and awireless mode of wireless equipment installed outside thethree-dimensional space.
 3. The wireless power-transmission apparatus ofclaim 1, wherein the antenna element is a phased array antenna having aplurality of antenna elements, the phased array antenna being capable ofadjusting the power transmission direction and a gain of the powertransmission beam, wherein the controller controls the powertransmission direction and the gain of the power transmission beam atthe phased array antenna so that the interference power of the powertransmission beam toward the outside of the three-dimensional spacebecomes equal to or smaller than the allowable value when the phasedarray antenna is disposed at the acquired inclination angle and height.4. The wireless power-transmission apparatus of claim 1, wherein thethree-dimensional space includes an indoor space having the antennaelement installed therein, wherein the controller controls at least oneof the antenna power and power transmission direction of the powertransmission beam so that the interference power of the powertransmission beam toward the outside of the three-dimensional spacebecomes equal to or smaller than the allowable value based on theinclination angle and height acquired by the acquirer, and shape andlayout information of the indoor space.
 5. The wirelesspower-transmission apparatus of claim 1, wherein the controller stopstransmission of the power transmission beam from the antenna elementwhen the interference power of the power transmission beam toward theoutside of the three-dimensional space does not become equal to orsmaller than the allowable value even though at least one of the antennapower and power transmission direction of the power transmission beam iscontrolled.
 6. The wireless power-transmission apparatus of claim 1further comprising an antenna adjuster to adjust at least one of theinclination angle and height of the antenna element, wherein thecontroller adjusts at least one of the inclination angle and height ofthe antenna element using the antenna adjuster, in addition to controlof at least one of the antenna power and power transmission direction ofthe power transmission beam, so that the interference power of the powertransmission beam toward the outside of the three-dimensional spacebecomes equal to or smaller than the allowable value.
 7. The wirelesspower-transmission apparatus of claim 1 further comprising aninterference power measurer to measure the interference power at an endof the three-dimensional space, wherein the controller controls at leastone of the antenna power and power transmission direction of the powertransmission beam so that the interference power measured by theinterference power measurer becomes equal to or smaller than theallowable value.
 8. The wireless power-transmission apparatus of claim 1further comprising: an angle measurer to measure an inclination angle ofthe antenna element; and a height measurer to measure a height of theantenna element, wherein the acquirer acquires the inclination anglemeasured by the angle measurer and the height measured by the heightmeasurer.
 9. The wireless power-transmission apparatus of claim 1further comprising a storage unit to store an inclination angle and aheight of the antenna element after installation or adjustment of theantenna element, Wherein the acquirer acquires the inclination angle andheight stored in the storage unit.
 10. A wireless power-transmissionmethod comprising: acquiring an inclination angle of at least oneantenna element to a plane direction of a reference plane and a heightof the antenna element to the reference plane, the antenna element beingdisposed at a specific position in a three-dimensional space having apredetermined shape and size, to transmit a power transmission beam; andcontrolling at least one of antenna power and a power transmissiondirection of the power transmission beam so that interference power ofthe power transmission beam toward an outside of the three-dimensionalspace becomes equal to or smaller than a predetermined allowable value,based on the acquired inclination angle and height.
 11. The wirelesspower-transmission method of claim 10, wherein the allowable value isset in accordance with a specification of and a wireless mode ofwireless equipment installed outside the three-dimensional space. 12.The wireless power-transmission method of claim 10, wherein the antennaelement is a phased array antenna having a plurality of antennaelements, the phased array antenna being capable of adjusting the powertransmission direction and a gain of the power transmission beam,wherein the controlling controls the power transmission direction andthe gain of the power transmission beam at the phased array antenna sothat the interference power of the power transmission beam toward theoutside of the three-dimensional space becomes equal to or smaller thanthe allowable value when the phased array antenna is disposed at theacquired inclination angle and height.
 13. The wirelesspower-transmission method of claim 10, wherein the three-dimensionalspace includes an indoor space having the antenna element installedtherein, wherein the controlling controls at least one of the antennapower and power transmission direction of the power transmission beam sothat the interference power of the power transmission beam toward theoutside of the three-dimensional space becomes equal to or smaller thanthe allowable value based on the inclination angle and height acquiredby the acquirer, and shape and layout information of the indoor space.14. The wireless power-transmission method of claim 10, wherein thecontrolling stops transmission of the power transmission beam from theantenna element when the interference power of the power transmissionbeam toward the outside of the three-dimensional space does not becomeequal to or smaller than the allowable value even though at least one ofthe antenna power and power transmission direction of the powertransmission beam is controlled.
 15. The wireless power-transmissionmethod of claim 10, further comprising: adjusting at least one of theinclination angle and height of the antenna element, wherein thecontrolling adjusts at least one of the inclination angle and height ofthe antenna element using the antenna adjuster, in addition to controlof at least one of the antenna power and power transmission direction ofthe power transmission beam, so that the interference power of the powertransmission beam toward the outside of the three-dimensional spacebecomes equal to or smaller than the allowable value.
 16. The wirelesspower-transmission method of claim 10, further comprising: measuring theinterference power at an end of the three-dimensional space, wherein thecontrolling controls at least one of the antenna power and powertransmission direction of the power transmission beam so that theinterference power measured by the interference power measurer becomesequal to or smaller than the allowable value.
 17. The wirelesspower-transmission method of claim 10, further comprising: measuring byan angle measurer, an inclination angle of the antenna element; andmeasuring by a height measurer, a height of the antenna element, whereinthe acquiring acquires the inclination angle measured by the anglemeasurer and the height measured by the height measurer.
 18. Thewireless power-transmission method of claim 10, further comprising:storing by a storage unit, an inclination angle and a height of theantenna element after installation or adjustment of the antenna element,Wherein the acquiring acquires the inclination angle and height storedin the storage unit.